Can phosphates in ICP appear higher than reality?

[Miami Reef]

Maybe because organics in the vial can break down in transit?

I use ICP to see how balanced the saltwater ions and trace metals are, but I also like to use ICP to see how well my test kits are preforming. I test my water the same time as I collect the sample for ICP.

Just wondering if nutrients can appear higher than reality.

 

[Randy Holmes-Farley Verified Community Expert]

ICP will detect organic P as P, as it will all other forms. No breakdown is needed. The super high temp plasma breaks it all down to atoms. the only thing not detect is any particulate form they somehow remove.

 

[Miami Reef]

ICP will detect organic P as P, as it will all other forms. No breakdown is needed. The super high temp plasma breaks it all down to atoms. the only thing not detect is any particulate form they somehow remove.

Thanks. I use ATI for ICP. These were my results from a few months ago.

I had an old phosphorus ULR test my PO4 at 0.04ppm while ICP tested at 0.08ppm.

Are you sure the phosphate of 0.08 was including organic P?

 

[Randy Holmes-Farley Verified Community Expert]

A number of folks have found issues between ICP of P and home phosphate tests, and the thought is two fold:

1. ICP is not that accurate for P.

2. Processes in transit impact the P in the water (algae or bacteria on the vessel sides take it up, for example).

 

[Dan_P]

Maybe because organics in the vial can break down in transit?

I use ICP to see how balanced the saltwater ions and trace metals are, but I also like to use ICP to see how well my test kits are preforming. I test my water the same time as I collect the sample for ICP.

Just wondering if nutrients can appear higher than reality.

The only way to test your test kit performance is with a standard. This is one of those really and truly black and white rules we are stuck with.

 

[Miami Reef]

The only way to test your test kit performance is with a standard. This is one of those really and truly black and white rules we are stuck with.

Thank you. I thought ICP would get me somewhat close. Whoops.

I did make a DIY alk standard and it was so helpful.

For calcium, I need to buy one.

Phosphates and nitrates: I pretty much trust the test kits, but I am curious to know how close the values are to reality.

 

[Dan_P]

Thank you. I thought ICP would get me somewhat close. Whoops.

I did make a DIY alk standard and it was so helpful.

For calcium, I need to buy one.

Phosphates and nitrates: I pretty much trust the test kits, but I am curious to know how close the values are to reality.

If you get really curious, you can determine how fussy a test kit is about sample volumes. By adding more or less than the required volume, you can determine how close the result is when you don’t add the exact amount. Might let you sleep better at night not worrying about it

 

[Miami Reef]

If you get really curious, you can determine how fussy a test kit is about sample volumes. By adding more or less than the required volume, you can determine how close the result is when you don’t add the exact amount. Might let you sleep better at night not worrying about it

I have a calibrated jewelry scale with an accuracy of +/-0.1

I rinse my vials with RO/DI 3 times
Then I rinse with tank water 3 times
Then I shake off excess and place vial on scale, add DT water with syringe until the scale shows 10.0g

I use a timer to count exactly 2 minutes of shaking (as per instructions).

I try my best to preform all my tests accurately. Our hobby grade kits aren’t 100%, so I try to do the best I can to get as close to accurate as possible.

I thank my chemistry lab for teaching me the proper way to doing tests. It’s one of my enjoyments of reefing lol.

 

[Dan_P]

I have a calibrated jewelry scale with an accuracy of +/-0.1

I rinse my vials with RO/DI 3 times
Then I rinse with tank water 3 times
Then I shake off excess and place vial on scale, add DT water with syringe until the scale shows 10.0g

I use a timer to count exactly 2 minutes of shaking (as per instructions).

I try my best to preform all my tests accurately. Our hobby grade kits aren’t 100%, so I try to do the best I can to get as close to accurate as possible.

I thank my chemistry lab for teaching me the proper way to doing tests. It’s one of my enjoyments of reefing lol.

I don’t know what grade you received in chemistry lab but you definitely learned the material well. Kudos!

 

[rtparty]

In real world experience, it makes no difference if you're at .04 or .08. You are basically within margin of error there.

So long as the home test is repeatable, that is all that matters

 

[gbroadbridge]

I have a calibrated jewelry scale with an accuracy of +/-0.1

I rinse my vials with RO/DI 3 times
Then I rinse with tank water 3 times
Then I shake off excess and place vial on scale, add DT water with syringe until the scale shows 10.0g

I use a timer to count exactly 2 minutes of shaking (as per instructions).

I try my best to preform all my tests accurately. Our hobby grade kits aren’t 100%, so I try to do the best I can to get as close to accurate as possible.

I thank my chemistry lab for teaching me the proper way to doing tests. It’s one of my enjoyments of reefing lol.

You know, the Hanna LR phosphate test is not supposed to be shaken, just inverted back and forwards until the reagent has dissolved after two mins.

The HR Nitrate on the other hand, is supposed to be vigorously shaken.

 

[Miami Reef]

You know, the Hanna LR phosphate test is not supposed to be shaken, just inverted back and forwards until the reagent has dissolved after two mins.

The HR Nitrate on the other hand, is supposed to be vigorously shaken.

Thank you!

 

[Miami Reef]

In real world experience, it makes no difference if you're at .04 or .08. You are basically within margin of error there.

So long as the home test is repeatable, that is all that matters

Very true.

 

[mbmartin06]

You know, the Hanna LR phosphate test is not supposed to be shaken, just inverted back and forwards until the reagent has dissolved after two mins.

The HR Nitrate on the other hand, is supposed to be vigorously shaken.

Assuming we are talking about the HI 774 the directions say shake and the video provided by hanna shows shaking. Did I miss an update?

 

[gbroadbridge]

Assuming we are talking about the HI 774 the directions say shake and the video provided by hanna shows shaking. Did I miss an update?

Well, the instructions say to shake gently.

However when I had a Hanna tech rep on site, he told me that means just invert end to end over and over until the reagent is dissolved and then keep going until 2 mins is up.

You don't want to introduce air into the sample if it can be avoided.

Sometimes I think the scientific staff and the marketing staff who make the videos live on different planets.

I tend to trust the technical types rather than the marketing gurus.

 

[mbmartin06]

Well, the instructions say to shake gently.

However when I had a Hanna tech rep on site, he told me that means just invert end to end over and over until the reagent is dissolved and then keep going until 2 mins is up.

You don't want to introduce air into the sample if it can be avoided.

Sometimes I think the scientific staff and the marketing staff who make the videos live on different planets.

I tend to trust the technical types rather than the marketing gurus.

makes sense really. I’ll try the invert next time. Tech and sales/marketing are really never on the same page. Thanks for the info.

 

[fryman]

Randy would know better but I believe ICP will detect inorganic & organic phosphate while home test kits only pick up inorganic phos.

I sent phyto culture water into ICP once. I used a centrifuge to remove the phyto.

Nitrate levels matched my test kit result but I measured 0 ppb phosphorus using hanna ulr while ICP measured elevated phos.

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*edit* oops, Randy already posted this. Sorry I should have read the thread first.

 

[mbmartin06]

Well, the instructions say to shake gently.

However when I had a Hanna tech rep on site, he told me that means just invert end to end over and over until the reagent is dissolved and then keep going until 2 mins is up.

You don't want to introduce air into the sample if it can be avoided.

Sometimes I think the scientific staff and the marketing staff who make the videos live on different planets.

I tend to trust the technical types rather than the marketing gurus.

I started using the inverting method as you described. A few tests in, it seems fine, and I don’t have to “flick“ the bottle to get rid of bubbles. Thanks for the advice.

 

[gbroadbridge]

I started using the inverting method as you described. A few tests in, it seems fine, and I don’t have to “flick“ the bottle to get rid of bubbles. Thanks for the advice.

You're most welcome.

Happy reef keeping